def to_bin(k):
  return bin(k)[2:]

def main():
  N = int(input())

  if(N == 1):
    print(0)
    return

  N_bin = to_bin(N)

  N_bin_len = len(N_bin)

  if int(N_bin[1:], 2) == 0:
    N_bin_len -= 1

  print(N_bin_len)

main()